Chlorinated isocyanuric acids are chemically stable solid compounds and are easy to handle. When dissolved in water, they are hydrolyzed to release active chlorine having a bactericidal activity. Since the active chlorine is excellent in stability and the bactericidal performance persists over a long period of time, the compounds are widely used as a bactericidal disinfectant for pool water, sewage water, and effluent from a human-waste treatment plant and as an algicide or an algae-proofing agent for cooling water of machinery and equipment.
As such chlorinated isocyanuric acid compounds, representative compounds include trichloroisocyanuric acid, dichloroisocyanuric acid, sodium dichloroisocyanurate and hydrates thereof, and potassium dichloroisocyanurate.
Among the chlorinated isocyanuric acid compounds, trichloroisocyanuric acid has the most high effective chlorine content of about 90% but the solubility in water is low as 1.2 g and hence the dissolution rate is slow, so that the compound is suitable for supplying a small amount of active chlorine over a long period of time but cannot be used for so-called superchlorination wherein water for a pool is treated with a high concentration of active chlorine prior to use.
On the other hand, since sodium salt or potassium salt of dichloroisocyanuric acid has a large solubility in water of about 25 g and a fast dissolution rate, it is suitable for the application of supplying a high concentration of active chlorine but it has a disadvantage that the effective chlorine content is low as about 60% and thus a large amount of the agent should be used.
In order to improve such problems, there is proposed a bactericidal disinfectant tablet wherein trichloroisocyanuric acid and sodium salt of dichloroisocyanuric acid are mixed (for example, JP-A-51-139628 and JP-A-53-136520).
However, since such a tablet is highly hygroscopic, there arises a problem that it is chemically decomposed during storage to generate chlorine gas. Moreover, when immersed in water, the tablet swells and disintegrates, but a satisfactory dissolution rate is not yet obtained.
Furthermore, JP-A-54-160730 proposes a tablet wherein trichloroisocyanuric acid and an alkali metal salt of cyanuric acid as a disintegrating agent are mixed. This tablet is excellent in storage stability but a satisfactory quick-dissolution is not yet attained and it has a disadvantage that an effective chlorine content is low.